The inline-five continues to produce a wicked soundtrack.

Audi Sport has vastly expanded its portfolio by slapping the RS badge on quite a few SUVs, as small as the RS Q3 and as large as the RS Q8. That doesn’t mean Ingolstadt’s go-faster division has been ignoring its traditional models as a new RS3 is right around the corner. It has been spotted obsessively while undergoing testing in both hatchback and saloon body styles, with the latest video showing the four-door model.

The high-powered RS3 compact saloon can be seen at full tilt working out at the Nürburgring gym. The camouflage is a bit pointless because we can basically see the whole car, complete with chunky air intakes and a subtle spoiler lip on the boot lid. It sits closer to the road thanks to a stiffer suspension setup and is hiding a larger set of brakes to match the beefier powertrain.

Gallery: 2021 Audi RS3 Sedan Nurburgring New Spy Photos

In typical Audi fashion, the Mercedes-AMG CLA 45 rival looks rather restrained, up to the point it’s almost a sleeper. However, if you know where to look, the RS upgrades are there. From the bulging wheel arches and bigger wheels to those enlarged air intakes and oval exhaust tips, there’s no denying this is the version positioned at the top of the food chain.

The main difference between the RS3 and its lesser counterparts will be the engine. Much like the RS Q3 / RS Q3 Sportback, the new A3-based dynamic duo will rock the same turbocharged inline-five unit. Audi hasn’t said how much power it will deliver, but the 2.5 TFSI is good for 394 bhp (294 kilowatts) and 354 pound-feet (480 Newton-metres) in the two potent crossovers and the TT RS.

We’ve been hearing some rather juicy rumours about Audi Sport’s desire to massage the five-cylinder engine to extract 415 bhp and 369 lb-ft (500 Nm). Per Auto Motor und Sport, an RS3 Performance will reportedly take the sweet-sounding powertrain to as much as 450 bhp, but nothing is official. For the time being, AMG holds the power crown with its “A45 S” models pumping out a meaty 416 bhp and 369 lb-ft (500 Nm) from a smaller 2.0-litre engine.

As to when we’ll get to check out the new RS3 models, it shouldn’t be too long. Audi Sport’s Sales and Marketing chief, Frank Michl, told Auto Express it would take “some months” until the world premiere, but that statement was made at the end of June. If we won’t see them before the end of this year, our money is on a world premiere in the first months of 2021.